Preliminary reports coming from the NTSB investigation of Monday’s Metrorail crash are indicating they’ve located a faulty computer circuit along that particular stretch of track. While the officials are reluctant to say it’s broken, they have indicated there were several “anomalies” coming from one particular circuit. According to a WTOP report on the air this morning, an internal WMATA memo indicated that the computer system may have sent the “all clear” signal instead of a “train ahead, all stop” one. An “all clear” signal would accelerate the train to the track’s top speed; in this area, it’s 59 mph.
When at that speed, the operator may not have seen the stopped train ahead in time for the emergency brakes to stop the six-car train. Fully loaded trains of that length weigh around 300 tons and need a good distance to brake.
Metro is still running trains on manual control, which gives the operators greater control over their cars. They will be working in such a mode for the foreseeable future.
The NTSB continues to stress their investigation may take over a year before arriving at a conclusive result and that the anomalies are only one discovery so far in their preliminary work.